In the operation of internal combustion engines, a number of operational and pollution problems have been encountered. Gasoline engines are a major source of air pollution including hydrocarbons and nitrous oxides. Diesel engines are subject to significant loss of oil, generate undesirable air pollution and are noisy in operation. To reduce air pollution, vehicle and engine design has been changed to provide catalytic converters for exhaust gases and blowby mechanisms for capturing emissions from crankcase breathers and recycling them back into the air intake system for the engine.
In gasoline engines, pollution control laws have mandated the engine emissions be reduced, and prevented from venting to the atmosphere. Engine exhaust must be cleaned and rendered environmentally safe. As a result, such advances as unleaded fuels and catalytic converters have been developed. Blowby devices such as pollution control valves (PCV) have become required standard equipment for all automobiles. These blowby devices capture emissions from the crankcase and communicate them in a closed system to the air intake system for the automobile. Here the emissions are mixed with incoming air before being introduced into the carburetor.
Because emissions from diesel engines are heavily laden with oil and other heavy hydrocarbons, air-oil separators such as are described and claimed in U.S. Pat. Nos. 4,274,807 and 5,140,957 have been developed. Such devices silence and filter air in an input flow line to an engine, separate oil and other hydrocarbons emitted from a contaminated engine atmosphere and regulate the pressure within the engine.
A recurrent problem encountered in engine operation, be it gasoline or diesel, is that a vacuum is created within the crankcase when the engine induction (air intake) system becomes fouled or malfunctions. This problem is magnified at high engine RPM's. It is important therefore that steps be taken to limit and/or prevent such vacuum from being created. Left unattended, the vacuum buildup tends to extract oil and other pollutants from the engine and can result in engine malfunction, safety problems and significant engine damage.
If the amount of vacuum is not controlled, a significant amount of oil and oil laden air will be pulled from the crankcase into the induction system of the engine or into the air-oil separator. The problem becomes more acute in cases where the air filter or separator becomes fouled or contaminated. When this occurs, the suction created by a turbocharger or the induction system of the engine increases the pressure differential between the breathers and the induction system thus increasing the vacuum in the crankcase.
A need therefore exists to provide a mechanism for exerting control over the amount of vacuum in the crankcase and limit it to a certain predetermined maximum.